1. Field of the Invention
This invention generally relates to power-driven angiographic syringes, and specifically to a plunger for such a syringe, and to the syringe and power injector system comprising same.
2. Description of the Related Art
In the field of angiography, a contrast medium of suitable indicating character (radiopacity) is introduced under pressure into coronary arteries, and the arterial network then is monitored by fluoroscopic or other visualizing means. As a result, arterial plaque deposits and/or other arterial occlusions are readily visually determined as to their size and location, so that suitable treatment methods, such as removal of the occluding material by lasing or mechanical excision, or displacement techniques such as balloon angioplasty, may be carried out.
To effect the introduction of the contrast medium into the arterial network for angiographic study, it has been common practice to utilize injector syringes in combination with arterial catheters. The syringe may be machine-mounted in a so-called "power injector" apparatus, with the distal end of the syringe being connected to the catheter which is introduced into the arterial system to be studied.
There is disclosed in U.S. Pat. No. 4,677,980 issued July 7, 1987 to D. M. Reilly, et al, an angiographic power injector featuring a rotating turret for housing multiple angiography syringes in readiness for injection. In use, the turret is selectively rotated to align an angiographic syringe with a driving mechanism of the power injector. Specifically, as is shown in FIGS. 9 and 10 of this patent, the plunger of the angiographic syringe may be configured wit rearwardly extending hook members which are engaged by the head and stem portion (typically termed a "ram" in the field) of the driving mechanism.
In the plunger configuration disclosed in this patent, the hook elements on the proximal face of the plunger are diametrically opposed to one another, to form a slot therebetween through which the ram head is inserted and subsequently rotated, the head being of transversely extending character, so that it thereby engages the respective hook members. In this manner, the head and stem of the driving mechanism and the hook members are described to constitute a quick release driving connection, with the driving mechanism head fitting into the aperture formed by the hook members, and with the stem extending out from the aperture through the access slot between the hook members.
The Reilly et al patent, at column 6, lines 24-52 thereof, describes the subsequent operation of the coupled syringe. First, the driving mechanism is forwardly translated to drive the plunger through the syringe to expel air therefrom. Next, the syringe is connected to a source of contrast media and the driving mechanism is retracted to pull the plunger back through the syringe, to draw contrast media thereinto. Finally, the driving mechanism is advanced to drive the plunger distally in the syringe and effect injection of the contrast media through a catheter attached to the syringe. The patent states that after the injection has been carried out, the driving mechanism may be disengaged from the plunger, without reversing its movement, by the simple expedient of rotating the driving mechanism 90.degree., so that the driving mechanism head extends from the aperture on either side (see FIG. 10 of the patent). Subsequent retraction of the driving mechanism results in the head and stem of the driving mechanism being withdrawn from the aperture and slot thereby disengaging he driving mechanism from the plunger.
As a result of the foregoing configuration of the driving mechanism, and the hook members on the plunger, the risks incident to retracting the plunger through the syringe during the angioplasty procedure are said to be eliminated, and the mating hook members and driving mechanism head are said to cooperate so that the plunger can be placed in either a driven retractable state, or an undriven non-retractable state, at any time during the injection operation and at any position of the plunger, without substantial force being applied therebetween.
While the foregoing configuration of the hook members on the plunger facilitates the engagement and disengagement of the driving mechanism, without change in the position of the plunger, it also is true that the hook members themselves provide only a very small contact area for mating with the head of the driving mechanism, when the driving mechanism is in driving or retraction engagement with the hook members.
There is thus the danger that the head of the driving mechanism may disengage from contact with the hook members during operation of the syringe, so that subsequent rotation of the driving mechanism to effect disengagement actually effects re-engagment of the driving mechanism with the hook members, in turn causing retraction of the plunger, an occurrence which specifically is desired to be avoided.
The Reilly et al patent discloses other plunger and driving mechanism constructions, e.g., as shown in FIGS. 11-21 of the patent, but all such alternative constructions are relatively more complex in construction and operation.
Prior copending U.S. patent application No. 07/299,974 filed Jan. 19, 1989 in the names of L. L. Densmore and T. A. Lindner, discloses an angiographic syringe plunger having a generally converging distal portion, and a rear face on which is provided a coupling structure which is transversely engageable by, and transversely disengageable from, a driving mechanism of a power-driven angiographic syringe. Once engaged by the driving mechanism, the plunger cannot be disengaged solely by rotation of the driving mechanism relative to the plunger in the absence of translational movement of the driving mechanism and plunger relative to one another. The coupling structure disclosed in this application includes a wall extending rearwardly from the proximal face of the plunger body and partially circumferentially thereon. The wall terminates at a proximal extremity, and a radially inwardly extending flange is joined at a outer peripheral portion thereof to the proximal extremity of the wall. In such manner, the radially inwardly extending flange and the wall form with the proximal face of the plunger a cavity transversely open to insertion of a ram head thereinto.
For example, the coupling structure described in this prior copending application may be generally C-shaped, with a continuously curved portion having an arc length not exceeding about 180.degree., and optionally provided with tangentially extending end segments respectively joined to the extremities of the continuously curved portion.
A disadvantage of the plunger construction described in copending U.S. patent application No. 07/299,974 is that the coupling structure thereof has a "directional" character, in that the plunger proximal face must be rotationally aligned with the head of the driving mechanism, to permit lateral engagement of the driving mechanism head with the cavity which is defined by the coupling means with the proximal face of the plunger. A corresponding orientation of the plunger and coupling mechanism likewise is required for lateral disengagement of the driving mechanism head from this cavity. As a result, this prior application discloses the use of registration marks on the plunger, for alignment thereof with a corresponding alignment mark on the carrousel of the power injector system (see, for example, FIG. 7 of this prior copending application, the disclosure of which hereby is incorporated herein by reference).
Even with such a registration system, however, the turret or carrousel arrangement employed on angiograpic syringe power injector systems necessitates that the ram access the plunger from two opposing directions. In other words, as the ram head is disengaged from the plunger of a first angiographic syringe in the carrousel, the carrousel is rotated to access a second angiographic syringe for engagement by the ram head. Since the ram head is engaging the respective first and second angiographic syringes from opposite directions, the plungers must be correspondingly "faced" in the proper engagement direction.
The directional difficulties associated with the provision of a multiplicity of angiographic syringes on a carrousel of a power injector system may thus be overcome by the above-described provision of alignment marks on the plunger and carrousel, however it may be difficult in practice to achieve the precise registration of alignment marks required for the effective use of the power injection system, particularly in use environments in which time is of critical importance.
Accordingly, it is an object f the present invention to provide a plugger which is readily engageable with the driving mechanism of a power injector system from both of two opposing directions.
It is another object of the present invention to provide an angiography syringe comprising such a plunger.
It is a further object of the present invention to provide an angiography power injector system comprising an angiography syringe including such a plunger.
Other objects and advantages of the present invention will be more fully apparent from the ensuing disclosure and appended claims.